The Bottom Line

Smoking during pregnancy – as well as exposure to second-hand smoke – increases the risks of many complications for both mother and baby. 

Nicotine travels from the mother to the fetus, affecting the developing brain and lungs, leading to potential neurological and pulmonary problems after birth. 

Tobacco smoke and its chemical make-up can affect gene regulation, decrease folic acid, and cause inflammation in the body – increasing the risk of complications such as miscarriage, fetal growth restriction, various birth defects, preterm labor, and even stillbirth. 

Pregnant women, and women trying to get pregnant, should talk to their HCP about options to help them quit smoking. There are several management techniques approved for pregnancy, and women should keep an open mind in trying these methods.

Women should also talk to their partner/family members who smoke and live in the same household.  Second-hand smoke can cause just as many complications during pregnancy, and couples/family members who quit together have better success.

Note: E-cigarettes are not a “healthier” alternative to smoking. Researchers are just beginning to identify adverse effects associating with vaping. Read more.

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Background

Smoking is a major public health issue and is one of the most harmful risk factors during pregnancy that can cause a wide range of possible complications.

In the United States (U.S.), up to 7% to 23% of pregnant women report smoking, but only an estimated 30% to 60% of those women stop smoking during pregnancy.

Tobacco smoke is a complex mixture of over 4,000 compounds that are genotoxic (causing genetic mutations) and carcinogenic (causing cancer); these compounds also cause heart disease, stroke, disability, and damage to every organ in the body as well as the immune system.

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Maternal and Fetal Effects

Evidence indicates the fetus can be affected by smoking at any stage of pregnancy, but that smoking cessation during pregnancy may decrease the risk of complications.

Smoking triggers inflammation and results in immune system dysfunction, both of which increase the risk for pregnancy complications.

When inhaled, nicotine can reach the brain within seconds. It passes through the placenta and enters the fetus at levels similar to or higher than the mother, affecting brain and lung development.

Nicotine and tobacco smoke are linked to the alteration of fetal brain structures, possibly due to DNA changes. Long-term outcomes in the infant/child include impaired intellectual development, learning deficits, and the development of attention deficit/hyperactivity disorder (ADHD).

According to a study published in May 2021, smoking more than 5 cigarettes daily during pregnancy increased the risk of offspring personality disorder as well as developing any Axis 1 psychiatric disorder, inclusive of mood, anxiety and psychotic disorders.

Smoking during pregnancy is also known to play a significant role in low birth weight, fetal growth restriction, delayed immune development, irregular sleep cycles, neonatal infection, childhood wheeze and asthma, kidney disorders, and birth defects of the cardiovascular and digestive systems, as well as cleft lip and cleft palate.

Smoking may be associated with four specific birth defects.

A study published in December 2020 identified four birth defects that were positively and significantly associated with maternal smoking: cleft palate, anomalies of the pulmonary artery, other specified anomalies of the mouth and pharynx, and congenital hypertrophic pyloric stenosis (Langlois et al. 2020).

Smoking may also cause complications early in pregnancy due to its effect on folate metabolism. Smoking decreases the amount of folate available in the body, and women who smoke may need additional folic acid supplementation during pregnancy.  Women should speak to their HCP prior to taking or increasing their folic acid intake during pregnancy.

Smoking and exposure to second-hand smoke also increases the risk of stillbirth and Sudden Infant Death Syndrome (SIDS), which are both assessed to be dose-dependent (the more a woman smokes, the more the risk increases).

A study published in May 2021 revealed that second-hand smoke exposure among nonsmoking women may alter DNA methylation in brain regions involved in development, carcinogenesis, and neuronal functioning of offspring. These findings further highlight potentially harmful effects on the epigenome of babies born to nonsmoking pregnant women who are exposed to tobacco smoke from family members or in the community.

There is also strong evidence that smoking can increase the risk of miscarriage, but is likely not a sole cause. Further, as many as 33% of all ectopic pregnancies are thought to be a result of smoking (due to inflammation).

The mother's risks of pregnancy-related complications also increase, to include placenta abruption, placenta previa, and premature labor. Breastfeeding may also be difficult as smoking is known to be associated with low prolactin levels.

Management

Smoking cessation during pregnancy has been found to reduce or even eliminate the risk of adverse pregnancy outcomes, including long-term outcomes. Most recommendations indicate that pregnant women should aim to quit smoking completely, rather than reducing the number of cigarettes.

Nicotine is highly addictive; it is also possible that nicotine clearance is higher during pregnancy, which can make quitting even harder. A combination of cessation techniques may be required for women attempting to quit during pregnancy.

Counseling: Behavioral intervention is a first-line treatment to help pregnant women quit smoking. HCPs can help recommend counselors during the first prenatal appointment (or ideally, a preconception appointment).

Nicotine Replacement Therapy (NRT): Food and Drug Administration–recommended pharmacotherapy products, including NRT, can be considered during pregnancy with close supervision of an HCP.

There is expert consensus that the nicotine provided via NRT is likely to be less harmful than smoking during pregnancy as it avoids other toxins that are inhaled in tobacco smoke.

Support: Women should find a circle of non-smoking friends who can offer emotional support to help them achieve their goal to quit smoking during pregnancy.

E-cigarettes are not a “healthier” alternative to smoking cigarettes.

E-cigarettes are not a “healthier” alternative to tobacco smoking as they contain numerous chemicals, flavoring components, and oils, in addition to nicotine. Recent research is only just beginning to identify the harmful effects of e-vapor and its flavoring components (read Vaping).

Action

Pregnant women, and women trying to get pregnant, should talk to their HCP about options to help them quit smoking. There are several management techniques approved for pregnancy.

Women who currently smoke and are concerned about their folic acid intake should talk to their HCP prior to increasing supplementation on their own.

Women should also talk to their partner/family members who smoke and live in the same household. Second-hand smoke can cause just as many complications during pregnancy, and couples/family members who quit together have better success.

Note: E-cigarettes are not a “healthier” alternative to smoking. Researchers are just beginning to identify adverse effects associating with vaping. Read more.

Partner/Support

It is very important for the health of the mother and her pregnancy that she is not exposed to second-hand smoke (SHS).  SHS exposure is associated with adverse birth outcomes such as low birth weight, stillbirth, preterm birth, miscarriage, and birth defects.

It is also assessed that SHS can pose a higher risk of pregnancy complications that mainstream smoke, as SHS is a combination of both, and therefore includes a higher number of chemicals than mainstream smoke alone.

Further, babies who are around cigarette smoke have weaker lungs, more breathing problems, and more infections than babies who are not around cigarette smoke.

If the mother quits smoking during pregnancy, there is a decrease in many of the associated risks.  However, at least one study noted that if the partner also quit, there was a much higher protective effect.

It is often recommended, for the long-term health of all involved, that the couple attempts to quit together during pregnancy (ideally, before pregnancy).

If a pregnant woman does not have a supportive partner, including a partner who smokes or who does not support her attempts to quit, complications can increase, along with emotional and possible depressive symptoms for the mother.

Resources

Smoking During Pregnancy (U.S. Centers for Disease Control and Prevention)

Tobacco and Nicotine Cessation During Pregnancy: Committee Opinion 807 (American College of Obstetricians and Gynecologists; May 2020)

It's Time to Quit Smoking (American College of Obstetricians and Gynecologists; June 2019)

Tobacco Use and Women’s Health: Committee Opinion 503 (American College of Obstetricians and Gynecologists)

Smoking and Pregnancy (U.K. Royal College Obstetricians and Gynaecologists)

Myths: Smoking and Pregnancy (SmokeFreeWomen)

Stop Smoking in Pregnancy (U.K. National Health Service)

Cigarette Smoke (MotherToBaby.org)

References

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